Size graders are used in the food industry for sorting a large number of food items, such as fruits or nuts, into various sizes. As examples, batches of shelled almonds, unshelled pistachios, raisins, and other foods may be sorted via size graders into bins holding items of similar sizes.
In the almond industry, a vibratory conveyor is vibrated or oscillated to convey shelled almonds down and along the length of the deck. The deck includes openings or holes sized to receive particular size product. There may be progressively larger holes down the deck, so that the smallest almonds fall through the first holes, the next size almonds fall through the next sets of holes, and so forth. Generally, larger grade almonds vibrate over and convey past the openings, and almonds of the particular opening size or smaller fall through the openings. The sorted almonds may then be further separated by vibratory decks having openings of different sizes. Thus, a size grader includes one or more vibratory decks having several different size round hole screens. As the almonds travel along the one or more decks, the almonds fall through the round holes separating them into various sizes. Although such round hole screens work well for their intended purpose, slow speeds and low volume through-puts must be used to allow the product to be properly directed to and fall through the proper size hole to be sorted into the appropriate size grades.